1. Field of the Invention
The present invention relates to image stabilization control technology that corrects or prevents image shake or image degradation occurring due to shakes such as hand shake.
2. Description of the Related Art
In recent years, all operations of a camera significant to image capture, such as the operation for determining the exposure and a focusing operation, may be performed automatically. Accordingly, even a user who is not accustomed to using a camera may nearly always succeed in taking high quality pictures. In addition, recently marketed cameras include an image stabilization control apparatus consisting of a shake correction unit, a driving unit, a shake detection unit, and the like and are configured to prevent image shake occurring due to shakes such as hand shake. A camera including an image stabilization control apparatus consisting of a shake correction unit, a driving unit, a shake detection unit, and the like almost eliminates the factors for inducing a shooting mistake by a photographer.
Here, an image stabilization control apparatus will be briefly described. The hand shake that may occur with a camera during image capture is a shake with a frequency of generally 1 to 10 Hz. To take a photograph without any image shake even when such hand shake is applied to a camera when the shutter release button is pressed, it is necessary to detect the angular rotational shake applied to the camera due to hand shake and displace a lens for correcting image shake (hereinafter simply referred to as a “compensation lens”) according to the detected value.
Meanwhile, when an image is taken at a close distance (under a capture condition in which a high imaging magnification is used), image degradation which caused by translational shake may not be ignored. For example, when an object image is taken at such a close object distance of about 20 cm in the case of macro photography, it becomes necessary to actively detect and correct the translational shake. Under capture conditions in which the focal length of an imaging optical system is very large (e.g., 400 mm) even when a sufficient object distance of 1 meter is ensured, it also becomes necessary to detect and correct the translational shake. However, translational shake may not be detected only by an angular velocity sensor and is applied to the horizontal direction or the vertical direction lying in a plane perpendicular to the optical axis of the camera.
Japanese Patent Laid-Open No. 7-225405 discloses a technology in which an accelerometer configured to detect acceleration is provided to detect translational shake by taking the second integral of the detected acceleration and drive a shake correction unit according to the detected translational shake value and an output from an angular velocity meter, which is provided separately.
Japanese Patent Laid-Open No. 2010-25962 discloses a technology in which translational shake is equivalent to angular rotational shake when the rotation center is located far from the camera.
The conventional method for performing translational shake correction using the rotation radius of angular rotational shake may cause the following circumstances.
For detecting translational shake in the horizontal direction of a camera, a yaw angular velocity sensor that is mounted for correcting yaw angular rotational shake and an acceleration sensor that detects acceleration in the horizontal direction of a camera are employed. A translational shake correction amount in the horizontal direction is calculated from the detected values obtained by both sensors. However, for translational shake in the horizontal direction of a camera, it is difficult to accurately determine a translational shake correction amount because the camera may be affected by translational shake associated with rotation of the camera in the roll direction in addition to translational shake associated with rotation of the camera in the yaw direction. In particular, when there is little rotation of the camera in the pitch direction and translational shake in the vertical direction associated with rotation of the camera in the roll direction is large, it is difficult to accurately determine a correction amount for translational shake in the vertical direction only by detecting the angular velocity in the pitch direction and the acceleration in the vertical direction. Note that the same applies to the detection of translational shake in the pitch direction.